1. Field of the Invention
The present invention relates in general to a fluid-filled cylindrical elastic mount used, for example, for mounting an engine of a front-engine front-drive motor vehicle, and more particularly to such an elastic mount which is improved in durability.
2. Discussion of the Prior Art
There is known a fluid-filled cylindrical elastic mount for damping radially applied vibrations in a certain frequency range, based on resonance of a mass of a non-compressible fluid existing in a restricted passage which communicates with a plurality of fluid chambers defined between an inner and an outer sleeve which are elastically connected to each other by an elastic body interposed therebetween. For instance, such a fluid-filled cylindrical elastic mount is used for flexibly supporting a power unit of a front-engine front-drive vehicle including an engine and a transmission, so that the body of the vehicle is isolated from vibrations of the power unit.
An example of the known fluid-filled cylindrical elastic mount of the type indicated above includes a cylindrical elastic body which elastically connects the inner and outer sleeves and which has a plurality of pressure-receiving fluid chambers formed therein so as to communicate with each other through a restricted passage. In the elastic mount having this construction, however, a part of the cylindrical elastic body is inevitably subjected to a tensile force while the elastic mount is in its operating state, namely, while the weight of a member to be supported, such as a power unit of the vehicle, acts on the elastic mount. Therefore, the elastic body of the known elastic mount tends to suffer from relatively low durability, resulting in accordingly low durability of the elastic mount. This means that the known elastic mount discussed above is not suitable as a mounting device which is permanently subjected to the weight of a certain load member such as the vehicle power unit indicated above.
Recently, there has been proposed an improved fluid-filled cylindrical elastic mount which includes (a) an inner sleeve, (b) an outer sleeve disposed outwardly of the inner sleeve, (c) an elastic body interposed between the inner and outer sleeves and having a pressure-receiving chamber filled with a non-compressible fluid, (d) means for defining an equilibrium chamber also filled with the non-compressible fluid, and (e) means for defining a restricted passage for restricted fluid communication or flow between the pressure-receiving and equilibrium chambers.
In the elastic mount constructed as described above wherein the equilibrium chamber communicating with the pressure-receiving chamber through the restricted passage is partially defined by the elastic wall, the elastic body need not be a cylindrical one and is therefore less likely to be subject to the tensile force due to the weight of a member to be supported. Thus, the instant arrangement prevents considerable reduction in the durability of the elastic mount in its operating state, providing an improvement in the durability of the elastic mount itself.
Although the improved fluid-filled cylindrical elastic mount indicated just above is less likely to be subjected to a tensile force due to the weight of a load member, the side wall portions of the elastic body which define the axial ends of the pressure-receiving chamber tend to have a considerably large compressive strain due to the weight of the load member, particularly when an applied vibrational load having a large amplitude is added to the weight of the load member. Such a compressive strain causes a decrease in the durability of the elastic body and the elastic mount.